1. Field of the Invention
The present invention relates to an electronic component such as, for example, a piezoelectric component and, more particularly but not exclusively, to a surface-mount type electronic component. The present invention also relates to a method of producing such an electronic part.
2. Description of the Related Art
A surface-mount type electronic component, specifically a piezoelectric component, of the type shown in FIGS. 1 and 2 is known. This electronic component incorporates an element 4 which makes use of piezoelectric vibration (referred to as "piezoelectric element"). The piezoelectric element 4 includes electrodes 4a and 4b disposed on upper and lower major surfaces thereof and is arranged to vibrate in a longitudinal vibration mode. Pattern electrodes 2 and 3 are provided on a substrate 1 which supports the piezoelectric element 4. The lower electrode 4b disposed on the lower major surface of the piezoelectric element 4 is connected and fixed to a first one 2 of the pattern electrodes by a conductive adhesive 5. The upper electrode 4a disposed on the upper major surface of the piezoelectric element 4 is connected to the other pattern electrode 3 by a wire 6. A cap 7 is attached to the upper surface of the substrate 1 so as to cover and seal the piezoelectric element 4.
In the piezoelectric component shown in FIG. 1, the upper electrode 4a of the piezoelectric element 4 and the pattern electrode 3 disposed on the substrate 1 are connected to each other by a wire bonding technique. It has been difficult, however, to optimize the wire-bonding process and resulting structural arrangement due to the difference in height or vertical location between the electrode 4a of the piezoelectric element 4 and the pattern electrode 3 disposed on the substrate 1.
When a capillary is moved while the wire 6 is being connected to one of these electrodes 3 and 4a, it is necessary to optimize the length of feed of the wire 6. If a feed length of the wire 6 is too small, the wire 6 may contact an edge of the piezoelectric element 4 as shown in FIG. 3, resulting in troubles such as cutting of the wire 6 or impairment of the electrical characteristics of the piezoelectric element 4. Conversely, if the feed length of the wire 6 is too large, this causes problems such as the wire 6 sagging downwardly as shown in FIG. 4, with the result that the wire 6 contacts the piezoelectric element 4 to impair electrical characteristics of the element 4.
For these reasons, mass-production of electronic components requiring wire bonding involves great manufacturing difficulty and experiences significant fluctuation of the quality.
Another problem is that the size of the electronic component must be large because of the need to provide a space between the substrate 1 and the cap 7 for accommodating the wire 6 which interconnects the upper electrode 4a of the piezoelectric element 4 and the pattern electrode 3 disposed on the substrate 1.
In the meantime, electronic components having lead terminals suffer from the following problem. In general, an electronic component, specifically of the type in which a circuit element is sealed with a resin without being constrained by the resin, has such a structure as that disclosed in Japanese Patent Publication No. 1-48695, wherein lead terminals are electrically connected to the corresponding electrodes of the circuit element and, after the circuit element is enclosed in a case with the lead electrodes extending externally through openings formed in the case wall, these openings are sealed by a sealing resin.
This type of structure, however, requires that different design configurations of the openings be provided in conformity with the shapes of the lead terminals, at the time of design of the products. In addition, it is necessary to apply a sealing resin to each of the openings in a one-by-one fashion. This causes an impediment to mass-production of the electronic parts, thus raising the costs of production.
Prior to the application of the sealing resin, since the lead terminals are directly connected to the circuit element, any load or external force tends to be directly transmitted to the circuit element, often resulting in breakage or cracking of the circuit element especially when the circuit element is a fragile one such as a piezoelectric element. Consequently, throughput is lowered and the number of acceptable components manufactured is substantially reduced.